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Melting Point and Molecular Symmetry

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R. J. C. Brown

Department of Chemistry, Queen''s University, Kingston, ON K7L 3N6, Canada

R. F. C. Brown

School of Chemistry, University of Melbourne, Victoria 3052, Australia

J. Chem. Educ., 2000, 77 (6), p 724

DOI: 10.1021/ed077p724

Publication Date (Web): June 1, 2000

Section:

History, Education, and Documentation

Abstract

In 1882 Thomas Carnelley observed that high molecular symmetry is associated with high melting point. The application of the rule to a number of different molecular crystals is discussed. The rule applies to different categories of crystal for different reasons, which can be explained by thermodynamic analysis. If the crystal is ordered, high melting point is usually due to high enthalpy change of fusion. If the crystal is disordered, high melting point is due to low entropy change of fusion. These effects can be displayed clearly on an enthalpy-entropy diagram.

Keywords (Audience):

Second-Year Undergraduate

Keywords (Domain):

History / Philosophy

Keywords (Subject):

Liquids

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This article has been cited by 16 ACS Journal articles (5 most recent appear below).

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